Quiz: Howstuffworks

Can You Get More Than 11 Right on This Physics Quiz?

Ryan Choate

Image: Martin Steinthaler/Moment/gettyimages

About This Quiz

Physics is the study of matter and energy and explains the natural phenomena of the universe. The study of physics began with the ancient Greeks, who wanted to understand the world around them. The field continued to evolve when, centuries later, Copernicus, Galileo and Newton added to our working knowledge of the universe. Copernicus brought us the heliocentric system. Galileo brought us the concept of inertia. And Newton provided us with three fundamental laws of motion.

However, physics extends beyond just classical mechanics. It also covers thermodynamics, electromagnetism, relativity and quantum mechanics. Some of the most modern discoveries have also been the field's most exciting. In 1998, scientists realized that the universe is expanding at an accelerating pace. A strange “dark energy” is driving this expansion. It's a theory right out of science fiction!

Then, even more recently, a group of scientists were able to detect gravitational waves. This is especially cool because Albert Einstein predicted the existence of these wrinkles in spacetime over a century ago. Einstein wasn't totally convinced that he was right, but now we have the equipment to detect these waves and prove that he was correct all along. Detection of these waves can allow us to “see” into the past and explain more of how we came into being. Pretty cool stuff!

Because physics is such a dynamic and fascinating field, it pays to know the basics. Can you answer at least 11 questions correctly?

Momentum is mass in motion. Which of the following objects does NOT have momentum?

A cyclist moving at a constant speed

The ISS orbiting the Earth

A dog running across a field

A broken down car sitting in the driveway

Momentum can be thought of as mass in motion. Therefore, if an object doesn't have both mass and velocity, then it does not have momentum. Since a broken-down car has a velocity of zero, it also has a momentum of zero.

What will an object that is more dense than water do when placed in a container of water?

Float

Sink

Dissolve

Suspend

The object (or fluid) with the greatest density will always sink to the bottom. This is why your salad dressing always separates. Oil is less dense than vinegar and sinks to the bottom of the container.

In the absence of air resistance, which object would fall to the ground the fastest?

Feather

Bowling ball

Baseball

They would all fall at the same rate.

If it weren't for air resistance, all objects would fall to earth at the same exact rate. The force of gravity acting on an object increases with that object's mass. That ensures that all objects maintain an acceleration of 9.81 m/s/s. Astronaut David Scott conducted an experiment on the moon, where he dropped a hammer and a feather. Both landed at the exact same time.

What is the lowest theoretical temperature possible?

Absolute Zero

-5,000 degrees Celsius

-5,0000 degrees Kelvin

0 degrees Celsius

At the theoretical temperature of absolute zero, atoms would stop moving. At this point, there is no kinetic energy, which is what creates heat in a substance. If there is nothing moving, then there is no heat. Absolute zero is equivalent to minus 273.15 degrees on the Celsius scale, minus 459.67 degrees on the Fahrenheit scale, and 0 degrees on the Kelvin scale.

What is the main factor that affects the speed of a sound wave?

Loudness of the sound

Pitch of the sound

Properties of the medium through which the sound is traveling

Amplitude of the sound wave

The speed of a wave is most dependent upon the properties of the medium a sound is traveling through, not the properties of the wave itself. Sound travels much faster through water than it does through air.

What ratio does density measure?

Mass to Weight

Mass to Volume

Inertia to Mass

Volume to Weight

Density is a measure of how tightly packed matter is. Density can be found by finding the mass of an object and dividing that by its volume.

A baseball is dropped from a 5-story window. Its gravitational potential energy before it is dropped is about 22 Joules. What is its kinetic energy when it hits the ground?

22 Joules

11 Joules

0 Joules

44 Joules

The total energy must remain the same. Since the ball begins with a potential energy of 22 Joules and a kinetic energy of 0 Joules (if there is no movement, then there is no kinetic energy), the total energy of the baseball is 22 Joules. As the ball falls, some of its potential energy is converted to kinetic energy. When it finally reaches the ground, all of its potential energy is converted to kinetic energy, making its kinetic energy 22 Joules.

When a rock is dropped, it will accelerate downward at a rate of 9.8 m/s/s. If the same rock is thrown downward, what will its acceleration be? (Ignore air resistance.)

9.8 m/s/s

More than 9.8 m/s/s

Less than 9.8 m/s/s

It depends on the direction of the throw.

The acceleration will still be 9.8 m/s/s. After the rock is thrown, the only force acting on it is gravitational force. This force creates an acceleration of 9.8 m/s/s.

What are the three primary colors of light?

Cyan, magenta and green

Orange, yellow and violet

Red, green and blue

Red, blue and yellow

The primary colors of light are red, green and blue. When red and blue light are combined, you will see magenta. When green and blue light are combined, you will see cyan. Red and green light combine to make yellow. And when all three primary colors of light are combined, you will see white light.

Energy comes in the form of kinetic energy and potential energy. Which object has the most kinetic energy?

A 50 kg object with a velocity of 4 m/s

A 10 kg object with a velocity of 10 m/s

A 20 kg object with a velocity of 5 m/s

A 100 kg object with a velocity of 1 m/s

The formula for kinetic energy is 1/2 times mass time velocity squared. Performing the calculations gives a kinetic energy of 500 joules for the 10 kg object moving at velocity of 10 m/s.

Sunsets have a reddish-orange color associated with them. Which phenomenon causes this?

Polarization

Diffraction

Dispersion

Refraction

When a beam of light strikes molecules in the atmosphere, it bounces off in different directions. This happens millions of times before the beam gets to your eyeballs. At sunset, the light takes a much longer path through the atmosphere to your eye than it does at noon. This creates that reddish-orange hue that we all see.

Two football players collide head-on. One football player has a mass of 60 kg. The other has a mass of 100 kg. Which player experiences a greater change in momentum?

The more massive player

The less massive player

They experience the same change in momentum.

There is no change in momentum for either player.

Each player experiences the same force, thanks to Newton's 3rd law of motion. They also experience this force for the same amount of time. This means that they experience the same impulse and the same change in momentum.

What is the groundspeed of an airplane that flies at an airspeed of 400 km/h in a 300 km/h hurricane crosswind?

400 km/h

300 km/h

500 km/h

700 km/h

When an airplane moves within a medium which is moving relative to the ground, the speed of the airplane(as measured by its speedometer) will not be the same as the speed as measured by a person on the ground (groundspeed). The groundspeed can be determined by adding the airplane's speed and wind speed as vectors.

What term describes the number of times a wave is generated per second?

Frequency

Wavelength

Amplitude

Trough

The number of waves produced each second is the frequency of the wave, measured in hertz. The frequency of a sound wave affects the pitch of the sound: the higher the frequency, the higher the pitch.

A truck traveling down the highway at 30 mph has a lot of momentum. What happens to its momentum if the truck doubles its speed to 60 mph?

Its momentum doubles.

Its momentum quadruples.

Its momentum remains unchanged.

Its momentum is zero.

Momentum is directly related to the velocity of an object. So for the same mass, a doubling of the velocity will lead to doubling the momentum.

A ball is dropped from rest from the top of a building. Assume negligible air resistance. Which force is acting on the object?

Gravitational

Tension

Applied

Spring

In the absence of air resistance, the only force acting upon the ball is gravity. Of course, if you do this on the moon, there will be less gravitational energy!

Your have a mass of 80 kg on the Earth. What is your mass on the moon?

13 kg

80 kg

40 kg

30 kg

Mass represents the amount of matter in an object. The amount of matter, and therefore the mass, does not change as it moves from location to another. So if you have a mass of 80 kg on Earth, you'll also have a mass of 80 kg on the moon.

What is the acceleration of a car that maintains a velocity of 60 mph for 10 seconds?

0 m/s/s

60 m/s/s

600 m/s/s

6 m/s/s

An acceleration is a change in velocity. If the velocity doesn't change, then there is no acceleration. Because of this, the acceleration of the car going 60 mph has an acceleration of zero.

Of the following, which is the most radioactive element?

Polonium

Radium

Uranium

Hydrogen

Radioactivity is a measure of how unstable an atom's nucleus is. An unstable nucleus sheds energy so that it can shift to a more stable configuration. Every element from 84 and up is radioactive, with no stable isotope. Polonium is so radioactive that it glows blue.

A skydiver has reached terminal velocity after jumping out of the plane. Which force is greatest?

Gravitational

Air resistance

Both are equal.

Some other force acts during terminal velocity.

Terminal velocity is reached when the force of air resistance reaches the same magnitude as the force of gravity. Once these forces are balanced, the skydiver no longer accelerates and will continue to fall at constant velocity.

Can you pick the Newton law that explains why airplanes accelerate forward when the propeller blows air backward?

1st

2nd

3rd

Law of Gravitation

Newton's 3rd law (For every action, there is an opposite and equal reaction) explains why a rearward force also results in a forward-facing force. The propeller pushes on the air, but the air pushes back on the plane, moving it forward.

Can you decide what requires more work: lifting a 20 kg crate a vertical distance of 3 meters or lifting a 30 kg crate a vertical distance of 2 meters?

Lifting the 20 kg crate

Lifting the 30 kg crate

Neither require work.

Both require the same amount of work.

The force of gravity acting on the 20 kg crate is about 200 N. The force of gravity acting on the 30 kg crate is about 300 N. %0DW = F x d%0DWork done on 20 kg crate = 200 x 3, which is about 600 Joules of work.%0DWork done on 30 kg crate = 300 x 2, which is also about 600 Joules of work.

All the following objects possess gravitational potential energy. Which has the most?

A 30 kg object at a height of 5 meters

A 10 kg object at a height of 10 meters

A 10 kg object at a height of 20 meters

A 100 kg object at a height of 1 meter

Gravitational potential energy is a product of mass, gravity, and height above the earth. Gravitational PE for a 10 kg object at a height of 20 meters is 2,000 Joules.

The following are all units of measure. Which unit is used to measure electric resistance?

Ohm

Ampere

Lumen

Joule

Some materials allow current to flow through better than others. A material's tendency to resist the flow of charge is called its resistance, and it's measured in ohms. 1 Ohm is the resistance between two points in a conductor where the application of 1 volt will push 1 ampere, or 6.241×1018 electrons.

Can you pick the example which does not demonstrate an acceleration?

A satellite circling earth at a constant speed

A ball speeding up as it is thrown

A ball slowing down as it is caught

A hockey puck sliding across ice in a straight line at a constant speed

Velocity is a vector quantity. This means that the direction is just as important as the magnitude when describing velocity. Therefore, any change in speed or direction is a change in velocity (and an acceleration). Since the hockey puck is maintaining constant speed and constant direction, it is NOT accelerating.

What is the name of the hydrogen isotope that contains 2 neutrons?

Deuterium

Tritium

Protium

Bietium

The nucleus of every hydrogen atom contains exactly one proton. However, the nucleus can also contain a varying number of neutrons. Protium is a hydrogen atom without any neutrons. Deuterium contains one neutron, and tritium contains two neutrons. Tritium is the most rare of the three isotopes, and also radioactive.

How many protons does a hydrogen atom have?

1

2

3

4

A neutral hydrogen atom contains exactly one proton and one electron. It is the simplest element in the universe and makes up about 75% of the baryonic mass of the universe.

What happens when you cut a bar magnet (with North and South ends) in half?

There'll be one North magnet and one South magnet.

There'll be two identical magnets - just smaller than the original.

It will no longer be a magnet.

The North and South ends will switch.

If you break a bar magnet in half, you'll get two smaller bar magnets. The North and South ends will arrange themselves in the following way: %0DBefore: N======S %0DAfter: N===S N===S

Physics quantities are either scalars or vectors. Which of the following quantities is a scalar?

Displacement

Velocity

Acceleration

Speed

Vectors require both magnitude and direction. Displacement, velocity and acceleration all express both magnitude (meters, m/s, and m/s/s) and direction, sometimes represented using negative or positive symbols. Speed describes a magnitude (m/s), but does not indicate a direction.

How many electrons does a positive ion have?

More than the neutral atom

Fewer than the neutral atom

The same number as the neutral atom

Exactly zero, no matter the ion

Because electrons are negatively charged, if an atom loses one (or more), it will become positively charged. On the flip side, if an atom gains electrons, it will become more negative.

What is the standard unit of measure for pressure?

Pascal

Watt

Newton

Meter

Pressure is defined as the amount of force exerted over a given area. You can create a lot of pressure by exerting a lot of force, or exerting a smaller force over a small area. This idea is why a magician can lie on a bed of nails: he total surface area of all the nail tips together is large enough.

A book resting on a table experiences a gravitational force pulling downward. What upward force is also exerted on the book?

Normal

Tension

Applied

Friction

The normal force will be as large as necessary to prevent the book from penetrating the table. Normal force gets its name because it refers to a perpendicular arrangement.

The atom is made up of particles with positive, negative or neutral charges. Which of the following has a positive charge?

Neutron

Proton

Electron

Photon

Protons are positively charged particles, located in the neutron of an atom. The number of protons in the nucleus determines the type of element an atom is, regardless of how many neutrons or electrons there are.

All but one of the following can be found in the nucleus of an atom. Which one doesn't belong?

Proton

Neutron

Electron

Quark

The nucleus of an atom is made of protons and neutrons. Protons and neutrons are made up of quarks. Electrons orbit the outer edge of an atom and are not found in the nucleus.

Can you pick the term used to describe the difference in charge between two points?

Voltage

Current

Resistence

Joule

Voltage is the difference in potential energy between two points in a circuit. This difference in energy creates pressure that forces charged electrons to flow in an electrical circuit.

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